Modulator block and electronic control brake system for vehicles having the same

ABSTRACT

Disclosed is brake system technology such as a modulator block and an electronic control brake system for vehicles having the same which suppresses residual frictional force generated due to contact between pads and a disc by moving a part of fluid at the wheel brake side to a residual frictional force control unit so as to retract pads from the disc, so that the hydraulic volume is reduced.

CROSS-REFERENCE TO RELATED APPLICATION

This application claims the benefit of Korean Patent Application No.2012-0032165, filed on Mar. 29, 2012 in the Korean Intellectual PropertyOffice, the disclosure of which is incorporated herein by reference.

BACKGROUND

1. Field

Embodiments of the present invention relate to an electronic controlbrake system for vehicles having a modulator block, and moreparticularly, to an electronic control brake system for vehicles havinga modulator block which prevents residual frictional force generatedbetween a disc and pads.

2. Description of the Related Art

In general, a vehicle is provided with a plurality of wheel brakes, eachof which includes a caliper device including a disc and a pair of padsto brake a front wheel or a rear wheel to decelerate or stop thevehicle, a booster forming brake hydraulic pressure and transmitting thebrake hydraulic pressure to the wheel brakes and a master cylinder, andthus, when a driver presses a brake pedal, the hydraulic pressure formedon the booster and the master cylinder is transmitted to pads of thewheel brakes, and the pads press the disc, thus generating brakingforce. However, when brake pressure is greater than a road surface stateor frictional force of the wheel brakes generated by the brake pressureis greater than braking force generated from tires or a road surfacewhile the driver presses the brake pedal to allow the vehicle to be in abraking force increasing state or a braking force maintaining state,slippage of the tires on the road surface occurs.

Recently, in order to effectively prevent such slippage to providestrong and stable braking force and to facilitate driving operation,brake systems, such as an anti-lock brake system (ABS) preventingslippage of wheels during braking, a traction control system (TCS)preventing excessive slippage of wheels during sudden start or suddenacceleration of a vehicle, and an electronic stability control system(ESC) or a vehicle dynamic control system (VDC) stably maintaining thedriving state of a vehicle by controlling a brake by combining an ABSand a TCS if the vehicle is not adjusted according to driver intentionby force applied from the outside during high-speed driving of thevehicle, have been developed.

These conventional brake systems for vehicles include in common amodulator block including a plurality of solenoid valves, accumulators,a motor and pumps to control brake hydraulic pressure transmitted towheel brakes, and an electronic control unit (ECU) to controlelectrically operated parts. The ECU senses a vehicle speed throughrespective wheel sensors disposed on front wheels and rear wheels, andthus controls operation of the respective solenoid valves, motor andpumps.

In the conventional brake systems, a disc of the wheel brake and a pairof pads pressing both sides of the disc may minutely come into contactdue to partial abrasion without generation of brake pressure duringdriving. Contact between the disc and the pads generates residualfrictional force and thus causes acceleration and driving loss.

SUMMARY

Therefore, it is an aspect of the present invention to provide anelectronic control brake system for vehicles which suppresses residualfrictional force generated due to contact between pads and a disc bymoving the pads away from the disc.

Additional aspects of the invention will be set forth in part in thedescription which follows and, in part, will be obvious from thedescription, or may be learned by practice of the invention.

In accordance with one aspect of the present invention, an electroniccontrol brake system for vehicles includes an electronic control unit, amaster cylinder, wheel brakes, plural NO type solenoid valves and NCtype solenoid valves, low pressure accumulators, pumps and a motor, andNC type shuttle valve, a TC solenoid valve, and a residual frictionalforce control unit. The electronic control unit may enable a control ofan anti-lock brake system (ABS) mode and a traction control system (TCS)mode. The master cylinder may form brake hydraulic pressure according tooperation of a brake pedal. Each of the wheel brakes may include acaliper device including a disc provided in a vehicle and advancing andretracting a pair of pads pressing the disc so as to exhibit wheelbraking force by the brake hydraulic pressure transmitted from themaster cylinder. The plural NO type solenoid valves and NC type solenoidvalves may respectively provided at upstream sides and downstream sidesof the wheel brakes and control the flow of the brake hydraulicpressure. The low pressure accumulators allow a fluid discharged fromthe wheel brakes to be temporarily stored therein during the ABS modebraking of the solenoid valves. The pumps and the motor may pressurizethe fluid stored in the low pressure accumulators so as to discharge thefluid to the wheel brakes or the master cylinder. The NC type shuttlevalve may be provided on an oil suction path connecting from the mastercylinder to an inlet of the pump so as to perform the TCS mode. The TCsolenoid valve may be provided between an outlet of the pump and themaster cylinder. The residual frictional force control unit may beprovided between the outlet of the pump and the TC solenoid valve. Theelectronic control unit may move a part of the fluid of a wheel brakeside to the residual frictional control unit to retract the pads fromthe disc.

The residual frictional force control unit may include an electroniccontrol valve and an actuator.

The electronic control unit may close the TC solenoid valve whileopening the electronic control valve to form a closed circuit sectionL1-1, and allow the closed circuit section L1-1 to communicate with aclosed circuit section L1-2, which is formed by opening the NO typesolenoid valve at the wheel brake side while closing the NC typesolenoid valve at the wheel brake side, so as to move the fluid in theclosed circuit sections L1-1 and L1-2 to the residual frictional forcecontrol unit.

In accordance with another aspect of the present disclosure, a modulatorblock includes plural NO type solenoid valves and NC type solenoidvalves, low pressure accumulators, pumps and a motor, an NC type shuttlevalve, a TC solenoid valve and a residual frictional force control unit.The plural NO type solenoid valves and NC type solenoid valves may berespectively provided at upstream sides and downstream sides of thewheel brakes and control the flow of the brake hydraulic pressure. Thelow pressure accumulators allow a fluid discharged from the wheel brakesto be temporarily stored therein during the ABS mode braking of thesolenoid valves. The pumps and the motor may pressurize the fluid storedin the low pressure accumulators so as to discharge the fluid to thewheel brakes or the master cylinder. The NC type shuttle valve may beprovided on an oil suction path connecting from the master cylinder toan inlet of the pump 13 so as to perform the TCS mode. The TC solenoidvalve may be provided between an outlet of the pump and the mastercylinder. The residual frictional force control unit may be providedbetween the outlet of the pump and the TC solenoid valve and include anelectronic control valve and an actuator.

A closed circuit section L1-1 formed by closing the TC solenoid valvewhile opening the electronic control valve may communicate with a closedcircuit section L1-2 formed by opening the NO type solenoid valve at awheel brake side while closing the NC type solenoid valve at a wheelbrake side. The actuator may allow a fluid in the closed circuit sectionL1-2 to move to the residual frictional force control unit through theclosed circuit section L1-1 that communicates with the closed circuitsection L2-1.

BRIEF DESCRIPTION OF THE DRAWINGS

These and/or other aspects of the invention will become apparent andmore readily appreciated from the following description of theembodiments, taken in conjunction with the accompanying drawings ofwhich:

FIG. 1 is a view schematically illustrating an electronic control brakesystem for vehicles in accordance with one embodiment of the presentinvention; and

FIG. 2 is a hydraulic circuit diagram of a modulator block of anelectronic control brake system for vehicles in accordance with oneembodiment of the present invention illustrating a closed circuitsection.

DETAILED DESCRIPTION

Reference will now be made in detail to the embodiments of the presentinvention, examples of which are illustrated in the accompanyingdrawings, wherein like reference numerals refer to like elementsthroughout.

FIG. 1 is a view schematically illustrating an electronic control brakesystem for vehicles in accordance with one embodiment of the presentinvention. With reference to FIG. 1, the electronic control brake systemfor vehicles includes a brake pedal 1, a booster 2 amplifying footeffort on the brake pedal 1 and outputting the amplified foot effort, amaster cylinder 3 converting pressure amplified by the booster 2 intohydraulic pressure, and a modulator block 6 connected to the mastercylinder 3 by a hydraulic pipe 4 and controlling transmission of brakehydraulic pressure to respective wheel brakes 5. Although notillustrated in detail, the wheel brake 5 includes a caliper deviceincluding a disc installed on a wheel, pads located at both sides of thedisc, and a piston advancing and retracting a cylinder to press the padsby brake hydraulic pressure.

FIG. 2 is a hydraulic circuit diagram of a modulator block of anelectronic control brake system for vehicles in accordance with thisembodiment of the present invention. In this embodiment, an electronicstability control (ESC) enabling a control of an anti-lock brake system(hereinafter, referred to as ABS) and a traction control system(hereinafter, referred to as TCS) will be exemplarily illustrated.

Generally, the master cylinder 3 includes two ports, i.e., a primaryport and a secondary port, each of which respectively controls two wheelbrakes of four wheel brakes (FR, FL, RR, RL), and each port is providedwith a hydraulic circuit. Since the configuration of the secondaryhydraulic circuit (not shown) is substantially the same as theconfiguration of the primary hydraulic circuit 10A, the primaryhydraulic circuit 10A will be described hereinafter and a repetitivedescription of the secondary hydraulic circuit will be omitted. However,a pump 13 provided on the primary hydraulic circuit 10A and a pump (notshown) provided on the second hydraulic circuit 10B are driven togetherwith a phase difference of 180 degrees by one motor 15.

As shown in FIG. 2, the primary hydraulic circuit 10A provided on themodulator block 6 includes plural solenoid valves 11 and 12 to controlbrake hydraulic pressure transmitted toward two wheel brakes 5 of a rearleft wheel RL and a front right wheel FR, the pump 13 sucking andpumping a fluid (oil) discharged from the wheel brakes 5 or a fluid fromthe master cylinder 3, a low pressure accumulator 14 temporarily storingthe fluid discharged from the wheel brakes 5, and an oil suction path toguide the fluid of the master cylinder 3 such that the fluid is drawntoward an inlet of the pump 13 during a TCS mode.

The plural solenoid valves 11 and 12 are connected to the upstream sidesand the downstream sides of the wheel brakes 5. The solenoid valves 11disposed at the upstream sides of the respective wheel brakes 5 arenormal open (NO) type solenoid valves which are maintained in an openstate at normal times, and the solenoid valves 12 disposed at thedownstream sides of the respective wheel brakes 5 are normal close (NC)type solenoid valves which are maintained in a closed state at normaltimes. The opening and closing operation of the solenoid valves 11 and12 is controlled by an electronic control unit (ECU; not shown) sensinga vehicle speed through wheel sensors (not shown) disposed at therespective wheels. For example, during pressure reduction braking, theNO type solenoid valves 11 are closed, the NC type solenoid valves 12are opened, and thus the fluid (oil) discharged from the wheel brakeside is temporarily stored in the low pressure accumulator 14.

The pump 13 is driven by the motor 15, sucks and discharges the fluidstored in the low pressure accumulator 14, and thus transmits fluidpressure to the wheel brakes 5 or the master cylinder 3.

In addition, an NC type electric shuttle valve (reference numeral: 16,hereinafter referred to as a NC type shuttle valve: ESV) is installed onan oil suction path, which is configured to guide the fluid of themaster cylinder 3 toward an inlet of the pump 13, so as to flow thefluid only toward the inlet of the pump 13. The shuttle valve 16 isclosed at normal times, and is open during the TCS mode.

In addition, an NO type solenoid valve (reference numeral: 17,hereinafter referred to as a TC solenoid valve) is installed on a mainpath connecting the primary port to an outlet of the pump 13 so as toperform a TCS mode control. The TC solenoid valve 17 is maintained in anopen state at normal times such that the brake hydraulic pressure formedat the master cylinder 3 is transmitted toward the wheel brake 5 throughthe main path during a normal braking operation through the brake pedal1, and also the solenoid valve 17 is closed by the electronic controlunit during the TCS mode control. Although not shown, a relief path anda relieve valve are provided between the oil suction path and the mainpath. The relief path and the relieve valve, during the TCS mode,returns the brake hydraulic pressure, which is discharged from the pump13, to the master cylinder 3, if the brake hydraulic pressure increasesabove a desired amount.

In addition, an electronic control valve 21 and an actuator 22 that forman residual frictional force control unit 20 are provided between thepump 13 and the TC solenoid valve 17 on the main path. The electroniccontrol valve 21 is provided in a NC type that does not operate during anormal braking operation, and the actuator 22 is provided using adiaphragm actuator. The diaphragm actuator 22 is driven by twoelectronic valves 23 and 24. The electronic valve 23 is connected to avacuum booster 25 such that the diaphragm actuator 22 is provided with avacuum suction force, and the electronic valve 24 is connected to theair such that the diaphragm actuator 22 is provided with a dischargingforce.

Hereinafter, the function and effects of the above-described electroniccontrol brake system for vehicles in accordance with this embodimentwill be described.

When slippage occurs during braking of a vehicle provided with such anelectronic control brake system, the ECU performs the ABS in threemodes, i.e., pressure reducing, pressure raising and pressuremaintaining modes, based on signals input from the respective wheelsensors. The respective ABS control modes of the four wheels FR, FL, RRand RL are not controlled identically but, rather, are controlledindividually according to road conditions and ABS control states. Now,the respective control modes will be described in stages through theprimary hydraulic circuit 10A.

First, in a state in which a driver presses the brake pedal 1 and thusbraking force is exhibited by fluid pressure generated by the mastercylinder 3, when brake pressure at the wheel brakes 5 connected to theprimary hydraulic circuit 10A is greater than a road condition (in thepressure reducing mode), the ECU executes an ABS pressure reducing modeby closing the NO type solenoid valves 11 and opening the NC typesolenoid valves 12 so as to reduce the brake pressure to a properpressure. Then, a part of fluid pressure (the fluid) is discharged fromthe wheel brakes 5 and is temporarily stored in the low pressureaccumulator 14, and the braking force of the wheel brakes 5 mounted onthe respective wheels is reduced and slippage of the vehicle on the roadis prevented.

When the ABS reducing mode is continued for a long time, vehicle brakingefficiency is lowered. Therefore, in order to increase fluid pressure ofthe wheel brakes 5, the ECU drives the motor 15, and thereby, an ABSraising mode is executed through fluid pressure discharged from the pump13 of the primary hydraulic circuit 10A. That is, the fluid stored inthe low pressure accumulator 14 is pressurized by the pump 13, and istransmitted to the wheel brakes 5 through the opened NO type solenoidvalves 11, thereby increasing brake pressure. Here, fluid pressuredischarged from the pump of the secondary hydraulic circuit is returnedto the master cylinder 3 or is transmitted to the wheel brakes connectedto the secondary hydraulic circuit according to brake pressureconditions.

If the brake pressure reaches a state generating the optimum brakingforce or the brake pressure needs to be maintained uniformly in order toprevent resonance of the vehicle, the ECU executes the ABS pressuremaintaining mode. The ABS pressure maintaining mode eliminatesfluctuation of pressure in the wheel brakes 5, and movement of hydraulicpressure is prevented by closing the NO type solenoid valves 11 of theprimary hydraulic circuit 10A. Here, fluid pressure discharged from thepump 13 is transmitted to the master cylinder 3, and thus the ABSpressure maintaining mode is stably executed.

Meanwhile, the above-described TCS is performed when the ECU sensesslippage, generated when a driver presses an acceleration pedal (notshown) deeply and thus the vehicle suddenly starts to drive on aslippery road, through wheel sensors. Then, during the TCS mode, the ECUopens the NC type shuttle valve 16 on the oil suction path, closes theTC solenoid valve 17 on the main path, and drives the motor 15 and thepump 13 to pump the fluid.

That is, when the TCS mode is executed, the fluid of the master cylinder3 side is sucked to the inlet of the pump 13 through the oil suctionpath, and the fluid discharged to the outlet of the pump 13 istransmitted to the wheel brakes 5 through the main path and the openedNO type solenoid valves 11 and acts as brake pressure. Consequently,when the driver presses the acceleration pedal for sudden start,designated lock is applied to the wheels even if the driver does notpress the brake pedal 1, and thus the vehicle slowly and stably startseven in slippery conditions, that is, under poor road conditions.

Meanwhile, during a constant speed mode driving such as a cruise, theelectronic control unit performs an active brake-pad retraction system(ABRS) mode that adjusts an interval between a disc and pads so as toprevent a residual frictional force from being generated due to thecontact between the disc and pads in a non-braking state, therebyenhancing the driving performance. That is, during the ABRS mode, theelectronic control unit moves a part of the fluid in the hydrauliccircuit at the wheel brake 5 so as to decrease the fluid pressure of thepiston pressing the pads such that the pads are retracted from the disc.

In detail, when the ABRS mode is executed, the ECU closes the TCsolenoid valve 17 and opens the electronic control valve 21 of theresidual frictional control unit 20, thereby forming a closed circuitsection L-1 at the outlet side of the pump (see the bold line at anupper side on FIG. 2). The closed circuit section L-1 communicates witha closed circuit section L-2 formed at the wheel brake side when the NOtype solenoid valve 11 and the NC type solenoid valve 12 are at a normalstate (see the bold line at a lower side on FIG. 2).

When the electronic valve 23 is operated and thus the actuator 22 isdriven, incompressible fluid at the closed circuit sections L-1 and L-2,in particular, the fluid at the closed circuit section L-2 at the wheelbrake side is moved to the residual frictional control unit 20 bypassing through the electronic control valve 21 that is open. As aresult, the fluid volume in the closed circuit section L-2 at the wheelbrake side is reduced, and thus the piston is retracted and the padsmove away from the disc.

Meanwhile, when the electronic valve 24 operates, the fluid in theresidual frictional force control unit 20 returns to the closed circuitsection L-2 at the wheel brake side due to the atmospheric pressure,thereby leading to a normal braking operation.

As is apparent from the above description, an electronic control brakesystem for vehicles moves a part of a fluid in a closed circuit section,which is formed by closing a partial section of a hydraulic circuit at awheel brake side in a hydraulic circuit of the entire system, to theoutside of the closed circuit by use of a residual frictional forcecontrol module to reduce the fluid volume at the wheel brake side,thereby retracting pads from a disc and effectively preventing residualfrictional force generated due to contact between the disc and the pads.

Although a few embodiments of the present invention have been shown anddescribed, it would be appreciated by those skilled in the art thatchanges may be made in these embodiments without departing from theprinciples and spirit of the invention, the scope of which is defined inthe claims and their equivalents.

What is claimed is:
 1. An electronic control brake system for vehiclescomprising an electronic control unit enabling a control of an anti-lockbrake system (ABS) mode and a traction control system (TCS) mode, amaster cylinder forming brake hydraulic pressure according to operationof a brake pedal, wheel brakes, each of which includes a caliper deviceincluding a disc provided in a vehicle and advancing and retracting apair of pads pressing the disc so as to exhibit wheel braking force bythe brake hydraulic pressure transmitted from the master cylinder,plural NO type solenoid valves and NC type solenoid valves respectivelyprovided at upstream sides and downstream sides of the wheel brakes andcontrolling the flow of the brake hydraulic pressure, low pressureaccumulators in which a fluid discharged from the wheel brakes istemporarily stored during the ABS mode braking of the NO type and/or NCtype solenoid valves, a pump and a motor pressurizing the fluid storedin the low pressure accumulators so as to discharge the fluid to thewheel brakes or the master cylinder, an NC type shuttle valve providedon an oil suction path connecting from the master cylinder to an inletof the pump so as to perform the TCS mode, a TC solenoid valve providedbetween an outlet of the pump and the master cylinder, and a residualfrictional force control unit provided between the outlet of the pumpand the TC solenoid valve, wherein the electronic control unit moves apart of the fluid of a wheel brake side to the residual frictionalcontrol unit to retract the pads from the disc.
 2. The electroniccontrol brake system for vehicles according to claim 1, wherein theresidual frictional force control unit comprises an electronic controlvalve and an actuator.
 3. The electronic control brake system forvehicles according to claim 2, wherein the electronic control unitcloses the TC solenoid valve while opening the electronic control valveto form a first closed circuit section, and allows the first closedcircuit section to communicate with a second closed circuit section,which is formed by opening at least one of the NO type solenoid valveswhile closing at least one of the NC type solenoid valves, so as to movethe fluid in the first and second closed circuit sections to theresidual frictional force control unit.
 4. A modulator block comprising:plural NO type solenoid valves and NC type solenoid valves respectivelyprovided at upstream sides and downstream sides of wheel brakes andcontrolling the flow of brake hydraulic pressure, low pressureaccumulators in which a fluid discharged from the wheel brakes istemporarily stored during the ABS mode braking of the NO type and/or NCtype solenoid valves, a pump and a motor pressurizing the fluid storedin the low pressure accumulators so as to discharge the fluid to thewheel brakes or the master cylinder, an NC type shuttle valve providedon an oil suction path connecting from the master cylinder to an inletof the pump so as to perform the TCS mode, a TC solenoid valve providedbetween an outlet of the pump and the master cylinder, and a residualfrictional force control unit provided between the outlet of the pumpand the TC solenoid valve and comprising an electronic control valve andan actuator.
 5. The modulator block according to claim 4, wherein: afirst closed circuit section formed by closing the TC solenoid valvewhile opening the electronic control valve communicates with a secondclosed circuit section formed by opening at least one of the NO typesolenoid valves at a wheel brake side while closing at least one of theNC type solenoid valves at a wheel brake side, and the actuator allows afluid in the second closed circuit section to move to the residualfrictional force control unit through the first closed circuit sectionthat communicates with the second closed circuit section.